Vandals

Three people are accused of vandalizing a police car, but possibly they aren't all guilty.
Guilty people are lying, while innocent people tell the truth. Who was/were the vandal(s)?

Larry says: "More than one of us vandalized the car."
Gary says: "Larry and Jerry did it."
Jerry says: "All three of us are guilty."

Answer

If Larry is lying, then the vandal has to be Larry alone. That means Jerry and Gary are telling the truth, but that would create contradictions. That means Larry must be telling the truth for there to be no contradictions. Since Larry is telling the truth, more than one person vandalized the car. Since it can't be Larry, it has to be Gary and Jerry.